From 7594bb08fb68ffe7e77c2e77ecc33c1e21631ead Mon Sep 17 00:00:00 2001 From: Johannes Thumshirn Date: Sat, 19 Dec 2020 00:35:25 +0900 Subject: [PATCH] Documentation: document dma device use for mcb Hannes reported a problem with setting up dma transfers on a mcb device. The problem boiled down to the use of a wrong 'device' for the dma functions. Document how to setup dma transfers for a IP core on a mcb carrier. Reported-by: Hannes Duerr Signed-off-by: Johannes Thumshirn Link: https://lore.kernel.org/r/3bdc8f76b30c2b0e2a2bfab06c2e73797ddc9384.1608305690.git.johannes.thumshirn@wdc.com Signed-off-by: Jonathan Corbet --- Documentation/driver-api/men-chameleon-bus.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/Documentation/driver-api/men-chameleon-bus.rst b/Documentation/driver-api/men-chameleon-bus.rst index 1b1f048aa748..6f0b9ee47595 100644 --- a/Documentation/driver-api/men-chameleon-bus.rst +++ b/Documentation/driver-api/men-chameleon-bus.rst @@ -18,6 +18,7 @@ MEN Chameleon Bus 4.1 The driver structure 4.2 Probing and attaching 4.3 Initializing the driver + 4.4 Using DMA Introduction @@ -173,3 +174,14 @@ module at the MCB core:: The module_mcb_driver() macro can be used to reduce the above code:: module_mcb_driver(foo_driver); + +Using DMA +--------- + +To make use of the kernel's DMA-API's function, you will need to use the +carrier device's 'struct device'. Fortunately 'struct mcb_device' embeds a +pointer (->dma_dev) to the carrier's device for DMA purposes:: + + ret = dma_set_mask_and_coherent(&mdev->dma_dev, DMA_BIT_MASK(dma_bits)); + if (rc) + /* Handle errors */